CVE-2026-33780
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA Missing Release of Memory after Effective Lifetime vulnerability in the Layer 2 Address Learning Daemon (l2ald) of Juniper Networks Junos OS and Junos OS Evolved allows an adjacent, unauthenticated attacker to cause a memory leak ultimately leading to a Denial of Service (DoS). In an EVPN-MPLS scenario, routes learned from remote multi-homed Provider Edge (PE) devices are programmed as ESI routes. Due to a logic issue in the l2ald memory management, memory allocated for these routes is not released when there is churn for these routes. As a result, memory leaks in the l2ald process which will ultimately lead to a crash and restart of l2ald. Use the following command to monitor the memory consumption by l2ald: user@device> show system process extensive | match "PID|l2ald" This issue affects: Junos OS: * all versions before 22.4R3-S5, * 23.2 versions before 23.2R2-S3, * 23.4 versions before 23.4R2-S4, * 24.2 versions before 24.2R2; Junos OS Evolved: * all versions before 22.4R3-S5-EVO, * 23.2 versions before 23.2R2-S3-EVO, * 23.4 versions before 23.4R2-S4-EVO, * 24.2 versions before 24.2R2-EVO.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA memory leak in Juniper's l2ald (Layer 2 Address Learning Daemon) fails to release memory allocated for ESI routes learned from remote multi-homed PE devices in EVPN-MPLS scenarios when those routes experience churn. This leads to progressive memory exhaustion until l2ald crashes and restarts, causing a Denial of Service.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 22.4= 22.4= 23.2= 23.4= 24.2< 22.4= 22.4= 23.2= 23.4= 24.2CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Adjacent
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Verify Junos versionRun 'show version' or 'request system version' to obtain the installed Junos or Junos OS Evolved versionAffected if The version matches < 22.4, = 22.4, = 23.2, = 23.4, or = 24.2 (i.e., not 22.4R3-S5, 23.2R2-S3, 23.4R2-S4, or 24.2R2+) and the device runs the l2ald daemon
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Confirm EVPN-MPLS is configuredRun 'show configuration protocols evpn' or 'show configuration protocols bgp | display set | match evpn' to check for EVPN protocol configurationAffected if EVPN protocol is configured and operating in MPLS mode (show evpn database extensive shows MPLS label entries)
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Check for ESI routes from remote multi-homed PEsRun 'show evpn instance <instance-name> extensive' or 'show route table evpn.0 | match ESI' to view ESI route entriesAffected if ESI (Ethernet Segment Identifier) routes learned from remote PE devices exist in the EVPN routing table, especially with frequent route churn
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Monitor l2ald memory consumptionRun 'show system processes internal l2ald' or 'show system memory' repeatedly over time and compare l2ald memory allocation trendsAffected if The l2ald process shows progressively increasing memory usage without returning to baseline, especially after EVPN route updates or churn events
A device is affected if it runs a vulnerable Junos version with EVPN-MPLS configured, has ESI routes from remote multi-homed PEs, and l2ald exhibits abnormal memory growth over time.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped22.4
Apply the vendor-supplied patches by upgrading Junos OS or Junos OS Evolved to one of the fixed versions (22.4R3-S5, 23.2R2-S3, 23.4R2-S4, or 24.2R2 and later). Monitor l2ald memory consumption using the provided command to confirm resolution.
Junos OS: 22.4R3-S5, 23.2R2-S3, 23.4R2-S4, or 24.2R2 (depending on current branch); Junos OS Evolved: 22.4R3-S5-EVO, 23.2R2-S3-EVO, 23.4R2-S4-EVO, or 24.2R2-EVO
- 1. Identify the current Junos OS or Junos OS Evolved version running on the device using 'show version'
- 2. Determine the appropriate upgrade path based on the current version branch (22.4, 23.2, 23.4, or 24.2)
- 3. For Junos OS: upgrade to 22.4R3-S5, 23.2R2-S3, 23.4R2-S4, or 24.2R2 (whichever is the next available release in the current branch)
- 4. For Junos OS Evolved: upgrade to 22.4R3-S5-EVO, 23.2R2-S3-EVO, 23.4R2-S4-EVO, or 24.2R2-EVO (whichever is the next available release in the current branch)
- 5. Download the appropriate upgrade image from Juniper Networks support portal
- 6. Upload the image to the device using 'request system software add <path-to-image>' or via USB
- 7. Reboot the device after upgrade completes using 'request system reboot'
- 8. After reboot, verify the fix by running 'show version' to confirm the new version is installed
Generated from the published advisory — verify against the referenced sources before acting.
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- Review / QA2.0 h
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-33780 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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